Obama: U.S. stands with Kenya after 'terrible outrage'

9/23/13 2:42 PM EDT

President Obama sent his condolences Monday to the people of Kenya, following a weekend terror attack at a mall in Nairobi.

"I want to express personally my condolences personally not only to President [Uhuru] Kenyatta, who lost some family members in the attack, but to the Kenyan people," Obama said while meeting with Nigerian President Goodluck Jonathan in New York. "We stand with them against this terrible outrage that's occurred."

Obama spoke with Kenyatta over the weekend, but his comments Monday were his first on camera. He didn't comment on reports that U.S. nationals were among the attackers in Nairobi, but did promise continued U.S. "cooperation" in the investigation of the attack.

The president also offered a hopeful take on the future of his father's homeland. "We are confident that Kenya, which has been a pillar of stability in eastern Africa, will rebuild," he said.

Deputy national security adviser Ben Rhodes said earlier Monday that the administration is looking into terror group al-Shabaab's claims that Americans were involved in perpetrating the attack, but is cautious. "We do monitor very carefully and have for some time been concerned about efforts by al-Shabaab to recruit Americans or U.S. persons to come to Somalia. So this is an issue that has been tracked very closely by the U.S. government, and it’s one that we’ll be looking into in the days ahead," he told reporters aboard Air Force One.